Noncorrosive insecticidal compositions



Patented Oct. 17, 1933 UNITED STATES PATENT OFFICE N ONCORROSIVE INSECTICIDAL COMPOSITIONS No Drawing. Application August 24, 1932 Serial No. 630,319

8 Claims.

The present invention relates to insecticidal compositions, which comprise barium fluosilicate as the active parasiticidal ingredient, which compositions have in aqueous suspension a p greater than about 4.0.

Barium fluosilicate has of late years become of great prominence as an insecticide.

In the practical application of this new insecticide as a spray in aqueous suspension, a serious difliculty has been met in that such aqueous suspensions of barium fiuosilicate were strongly corrosive, particularly toward certain types of spray pumps commonly used by large orchardists. Such pumps are constructed with cylinders of white enamel lined steel or cast iron and use rubber pistons. While such construction prevents rusting of the equipment while idle, itwas found that the enamel is rapidly destroyed when the pumps are used with barium fluosilicate sprays.

I .have found that the acidity of the barium fluosilicate sprays was responsible for the attack of the spraying equipment and I further found that a pH value of about 4.0 is the critical point below which there is substantial attack of the enamel, whereas sprays having a pH above 4.0 are practically inert towards the enamel lining of the spraying equipment in common use.

I have found in this investigation that practically every sample of even the purest barium fiuosilicate as manufactured by all processes known to me, when mixed with water to make a slurry or suspension of spray strength imparts to the suspension a pH value of approximately 3.7 or less, which is in the range of corrosive acidity. Addition of alkali to such sprays to neutralize this acidity is not possible as barium fluosilicate decomposes in the presence of alkali.

I have, however, found that the addition of relatively small amounts of a somewhat water soluble, ionizable and substantially neutral fluoride to barium fluosilicate suspensions raises the pH value of such suspensions above the critical limit for corrosiveness.

In the practice-of producing'a non-corrosive barium fluosilicate insecticide according to my invention, I mix with the barium fluosilicate or add to its aqueous suspension from about 5 to 10 or more per cent of a slightly water soluble, substantially neutral fluoride, such as sodium fluoride, barium fluoride, sodium-aluminum fluoride (otherwise called cryolite) etc. The solubility of these fluorides is given in the literature as follows, expressed in grams of the fluoride per 100 cc of solution at 25 C:NaF:4.05; BaFz:0.121; NaaA1Fa20.061. The fluoride used in my novel composition must be noticeably soluble in water to produce the desired effect, such solubility must at least be greater than that of for instance calcium fluoride which is 0.004 grams per 100 cc of solution at 25 C. 00

The following pH values have been obtained in aqueous suspensions corresponding to three pounds of the insecticide suspended in one hundred gallons of water, which is a common concentration for agricultural sprays.

Insecticide pH BaSiF. 100% a. 1-3. s

BaSiFu 95% 0 BBF: 5%

BaSiF 907 Bar, 10%

BaSiF B81, 4.2-4.4 Bar, 100% 7. 6-8.0

NaF 100% s.'2-s.4

Basil". 957 Na! 5% BaSiF 90 Na! 10%;

Basin 80% 4 8 M11 20% Naisiri 100% 1.2-1.0 86

BaSiFo 00% 4 2 Nam. 10%

BaSiFu s07 N zAlFu 20 7:

The pH of the water used in these tests was 7.4. It was found that in some mixtures the pH slightly increased during a period of several 1 hours as indicated in the above table where, in

several instances, a pH range is indicated. In the case of suspensions of barium fluosilicate and cryolite the pH of freshly prepared mixtures was considerably higher and the figures indicated for such suspensions represent the value obtained after about an hour's standing of the suspension from which time on the value remained substantially constant.

A theoretical explanation of the phenomena disclosed by the results of the above tests may be as follows:

Barium fluosilicate decomposes to a slight extent in aqueous solutions into BaFz and SiF4. This latter hydrolyzes then into S102 and 4H1 and this latter imparts to the aqueous solution the acidity indicated by the pH of 3.7 or 3.8 110 tion of barium fiuosilicate may therefor contain an equilibrium represented by the formula:

When I add to such a. system in equilibrium other fluorine ions the decomposition oi the barium fiuosilicate and/or the hydrolysis of the SiF4 is to a certain extent suppressed according to the mass action law and less free HF will be found in the system, as is indicated by the increased pH thereof. The concentration of the aqueous suspension is practically immaterial within the range of compositions used in agricultural sprays, as in each instance I obtain saturated solutions in the presence of the large excess of undissolved material.

A possible experimental confirmation of the above explanation can be found in my experiments in which I add barium carbonate to an aqueous suspension of barium fiuosilicate. Barium carbonate imparts to itsaqueoussuspensions a pH of 8.0, similar to that of sodium fluoride or barium fluoride and for purposes of this invention barium carbonate, barium fluoride and sodium fluoride can be considered to be substantially neutral.

Barium carbonate, when added to an aqueous suspension of barium fiuosilicate, reacts to form .barium fluoride as has been experimentally proven; the decomposition of the barium fiuo- Basin 4.0-4.2 132100; 5

BflSiFg 90% 4. 2-4. 4 13800; 10

BaSiFu 30 4.e4.s B8003 20% Such suspensions actually contain in their aqueous phase barium fiuosilicate and barium fluoride.

Aqueous suspensions prepared according to the proportions indicated in the above tests have been tried in commercial spray equipments and in all instances where the pH of the suspension was equal to or exceeded the value of 4.0 no 8 noticeable corrosion took .place.

I claim:

1. A non-corrosive insecticidal mixture comprising barium fluosilicate as the active parasiticidal ingredient and a substantially neutral 8 fluoride of a water solubility greater than that of calcium fluoride, said mixture having the property of imparting to its aqueous suspensions a pH of 4.0 and greater.

2. A non-corrosive insecticidal mixture com- 9 prising barium fiuosilicate as the active parasiticidal ingredient and barium fluoride, said mixture having the property of imparting to its aqueous suspensions a pH of 4.0 and greater.

3. A non-corrosive insecticidal mixture com- 9 prising barium fiuosilicate and aluminum-sodium fluoride, said mixture having the property of imparting to its aqueous suspensions a pH of 4.0 and greater.

4. A non-corrosive insecticidal mixture comprising barium fiuosilicate and barium carbonate, said mixture when suspended in water producing an aqueous phase containing barium fluoride, said aqueous phase having a pH of 4.0 and greater.

5. A non-corrosive agricultural-spray comprising an aqueous suspension of barium fiuosilicate and a substantially neutral fluoride of a water solubility greater than that of calcium fluoride, said spray having a pH of 4.0 and greater.

6. A non-corrosive agricultural spray comprising an aqueous suspension of barium fiuosilicate and barium fluoride, said spray having a pH of 4.0 and greater.

'7. A non-corrosive agricultural spray comprising an aqueous suspension of barium fiuosilicate and aluminum sodium fluoride, said spray having a pH of 4.0 and greater.

8. A non-corrosive agricultural spray compris- 12! ing an aqueous suspension of barium fiuosilicate and barium carbonate, said spray containing in its aqueous phase barium fluoride and having a pH of 4.0 and greater.

EARL B. ALVORD. 

